1. Technical Field
This disclosure relates to communication technology in which a master device is connected to one or more slave devices, and various kinds of information are exchanged as the slave devices respond to commands issued by the master device.
2. Background Art
There is a conventional communication system in which a plurality of devices having a master function of controlling transmission and reception of data are connected on a bus (a communication line), and various kinds of information are exchanged between the devices. With such a communication system, the control of a bus (hereinafter referred to as bus control) has to be determined between a plurality of devices having such a bus master function so that only one of the devices has the bus control at a time.
For example, FIG. 27 shows a communication system disclosed in US 20070186020 A1, in which a plurality of devices having a bus master function are connected by a bus. With this communication system, first, the device requesting the bus control embeds a bus control request in a response to a bus transaction from the device having the bus control. The device that detects the request then permits the device requesting the bus control to use the bus control after completion of the transaction.
In the example shown in FIG. 27, devices 1201a to 1201d having a bus master function are connected by a bus, and the device 1201a has the bus control. If the device 1201b requests the bus control, the device 1201b embeds a bus control request BusREQ in a response P122 to a bus transaction request P121 from the device 1201a. The device 1201a permits the device 1201b to use the bus control once it recognizes the bus control request included in the received response P122.